Journal of Applied Chemical Science International 9(2): 104-114, 2018 ISSN: 2395-3705 (P), ISSN: 2395-3713 (O) RHEOLOGICAL CHARACTERISTICS OF PETROLEUM JELLY FORMULATIONS CONTAINING ORGANICALLY MODIFIED LAYERED DOUBLE HYDROXIDES DAMODAR MOSANGI1,2,3, SREEJARANI KESAVAN PILLAI1*, LUMBIDZANI MOYO1 AND SUPRAKAS SINHA RAY1,2 1DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, 0001, Pretoria, South Africa. 2Department of Applied Chemistry, University of Johannesburg, Droonfontein 2028, Johannesburg, South Africa. 3AMKA Products Pty Limited, Innovation Building, 14 Ellman Street, Sunderland Ridge, Centurion 0157, Pretoria, South Africa. AUTHORS’ CONTRIBUTIONS This work was carried out in collaboration between all authors. Author DM designed the study, performed the experimental work and wrote the protocols. Authors SKP and LM managed the analyses, managed literature and wrote the first draft of the manuscript. Suprakas Sinha Ray reviewed and corrected the manuscript. All authors read and approved the final manuscript. ARTICLE INFORMATION Editor(s): (1) Nagatoshi Nishiwaki, Kochi University of Technology, Japan. (2) Ling Bing Kong, Nanyang Technological University, Singapore. Reviewers: (1) Ayi A. Ayi, Federal University, Nigeria. (2) Joel Obed Herrera Robles, Autonomous University of Ciudad Juarez, Mexico. (3) Margarita Teutli León, Benemerita Universidad Autónoma de Puebla (BUAP), Mexico. Received: 04 June 2018 Accepted: 20 August 2018 Published: 08 September 2018 Original Research Article __________________________________________________________________________________ ABSTRACT The effectiveness of stearic acid modified layered double hydroxides (OLDH) as viscosity modifier and stabilizer in petroleum jelly (PJ) formulations has been studied and its rheological properties evaluated. Mg-Al- LDH was organically modified using stearic acid which is anionic surfactant widely used in topical formulations. Successful incorporation of stearate anion into LDH interlayers was confirmed by XRD, FTIR, SEM, and TGA results. PJ formulations were prepared using different OLDH contents (0.5, 1, 1.5 and 2 wt. %) using a high shear mixer. The incorporation of OLDH significantly increased the viscosity of the PJ formulations which is explained by strong interaction between OLDH particles and hydrocarbon chains of PJ. The percolation threshold was observed to be at 1.5 wt.% of OLDH loading suggesting the presence of a well- developed interface between the filler and the polymer matrix. The non-Newtonian shear thinning indicated the formation of gel-like structure. Dynamic state rheological data of PJ formulations showed a dominance of elastic property imparted by solid phase in OLDH based system. OLDH, therefore, showed great promise as an efficient structural ingredient in cosmetic formulations offering viscosity enhancement as well as shear thinning behaviour which could result in formulation stability, better skin feel and spreadability. _____________________________________________________________________________________________________ *Corresponding author: Email: [email protected]; Mosangi et al.; JACSI, 9(2): 104-114, 2018 Keywords: Layered double hydroxide; organically modified layered double hydroxides; characterization; petroleum jelly; rheological properties. 1. INTRODUCTION describes topical compositions containing solid starch and hydrophobic starch. The invention claims that the Petrolactum (petroleum jelly (PJ) or Vaseline) is one inclusion of hydrophobic starch reduces the greasy of the ancient skin treatment products and are widely appearance and its resistance to washing although the used in cosmetics and pharmaceuticals industries [1]. rheological property of the formulation was not In pharmaceutical industry, PJ is used as a base investigated. material in a variety of topical ointment formulations to minimize various skin diseases. Its occlusive, as Layered double hydroxides (LDHs) are synthetic well as healing characteristics render this substance anionic clay minerals represented by the molecular x+ − particularly efficient against dry and damaged skin [2, formula M (1−x) M3x (OH)2) . (A )x. nH2O where M2, - 3]. Because of its lipophilic character, physical and M3 and A represent divalent, trivalent cations and chemical inertness, PJ is also used as an essential anions respectively [14]. They have well-ordered ingredient in many formulations of cosmetic products brucite like layer structure in which the cations are providing different types of skin care and protection octahedrally coordinated by six oxygen atoms as 2+ 3+ by minimising friction or moisture loss or by hydroxides. The substitution of the M with M ions functioning as a grooming aid [4]. imparts a net positive charge to the sheets which are compensated by exchangeable interlayer anions and PJ is chemically similar to mineral oil. While mineral water [15]. The intrinsic hydrophilic surface property oil contains mainly liquid hydrocarbons, PJ is a of LDHs can be modified through surface mixture of solid and liquid hydrocarbons (normal, iso modification or intercalation with anionic surfactants and ring paraffins) in the form of 3D gel structure and [16-19]. Organo-LDHs are oil compatible hence is in a solid state at room temperature [5]. PJ is hydrophobic organic compounds and hence could be thus considered as a soft microcrystalline wax with used as phase stabilizers and rheology modifiers in oil high oil content [6]. Although PJ is petroleum (fossil rich formulations. Focke et al. [20] showed strong fuel) based product, components derived from shear thinning behaviour and anomalous temperature synthetic sources can be added to overcome its dependence of jojoba oil containing stearic acid drawbacks such as greasiness and resistance to intercalated Mg-Al-LDHs. Naime Filho et al., [21] washing in cold soap and detergent solutions [7,8]. incorporated glycine or alanine modified LDHs into a However, in such formulations, obtaining the desired silicone matrix containing Dimethicone, PEG-8 stability, viscosity and 3D-network structure phosphate (PE-100) and obtained a drastic change in formation remain a challenge. Disruption of 3D- the rheological behaviour, due to an extensively network structure causes liquid components to developed gel-like structure for the nanocomposite separate from the heavier components leading to an derivatives. While shear-thinning nature was evident, unstable formulation. In such cases, ingredients the critical concentration was observed to be 5% that can act as binders are required to obtain a suggesting the presence of a largely developed stable formulation [8,9]. interface between the filler and the polymer. The increase in viscosity was explained by the rather The incorporation of synthetic additives can greatly strong attrition phenomenon between amino acid alter the rheological properties of PJ itself which is anions and the silicone chains. very crucial in deciding the quality and function of final products in cosmetics where PJ is used as a main Inspired by these early investigations, the objective of or supportive ingredient. The problems such as liquid this work is to study the effectiveness of stearic acid separation, lack of structure and required viscosity modified layered double hydroxides (OLDH) as a could be related to the poor dispersion of the internal binder/stabilizer in PJ formulation and to evaluate phase as well as the degree of shear sensitivity of PJ shear flow properties of corresponding formulations. formulation [9]. There have been many studies to The interest is to develop an improved PJ composition investigate the rheological properties of PJ during past in terms of flow properties, stability as well as colour decades [3, 10-12]. However, only a little attention and feel of the product on the skin. has been given to PJ compositions containing additives that could have great impact on its The use of organic modified layered double performance characteristics. The use of synthetic wax hydroxides (OLDH) in PJ products is largely components such as Fischer-Tropsch wax in unknown. OLDH is expected to provide petrolatum formulation that can alter the rheological multifunctional benefits such as thickening, a 3D- properties and hence the skin sensation has been network structure, prevention of phase separation, reported recently [13]. US patent 3852475 [7] colour and consistency through interaction of organic 105 Mosangi et al.; JACSI, 9(2): 104-114, 2018 surface layer with oil phase of the formulation. The Table 1. Composition of PJ formulations fact that no reference to OLDH in petroleum jelly formulations could be found in literature indicates that Entry Ingredients Percentage (%) the process and the product are unique. 1 Mineral oil Q.S. 2. EXPERIMENTAL 2 Microwax 10-27 3 OLDH 0.1-2.0 2.1 Materials 4 Paraffin wax 10-25 Hydrotalcite (Pural MG 70) of chemical formula 5 Amka wax 1 Mg2xAl2(OH)4x+4CO3.nH2O was supplied by Sasol Germany (referred to as LDH), which was 2.2.3 Characterization of OLDH synthesized by hydrolysis of hetero-metallic alcoholates. Stearic acid was supplied by Bio-zone X-ray diffraction (XRD) studies were conducted using chemicals, Kempton Park, South Africa. Distilled an X’Pert PRO X-ray diffractometer (PANalytical, water was used in all experiments. Other chemicals Netherlands) operating with Cu K-α radiation used were sodium dodecyl benzene sulphonate (Fluka (wavelength of 0.15406 nm) at 45 kV and 40 mA. The exposure time and scan speed